That problem is the linker not being able to link fltk into the GUI properly. Two things:

1) If you run "make obdsim", do you see similar errors, or does it build? [obdsim has an fltk module in it too]
2) If you don't care for the GUI, at least to start, re-run cmake with "-DOBD_DISABLE_GUI=ON" and it'll disable the GUI, allowing everything else to build.

As for the specific problem, please could you let me know what version of ubuntu you're on [including architecture], and what the output of "fltk-config --version --prefix" is ?

If not needed (i.e., not re-make), i execute "./obdsim -g Random 42".
and try to use my android phone to connect computer through Bluetooth.
It also doesn't work...

By the way, I use the software, "Torque", which is a famous engine diagnostics application for Android.
The following is the link for Torque.http://android-apps.com/applications/torque/
Therefore, it may not the problem of software.

P.S. If my OS is windows, any solutions to use obdsim through bluetooth interface?